Speed barometric altitude and airplane acceleration responsive fuel control



Jan. 16, 1951 s. M. UDALE 2,538,606

SPEED BAROMETRIC ALTITUDE AND AVIRPLANE ACCELERTION RESPONSIVE FUELCONTROL.

Jan. 16, 1951 s. M. UDALE 2,538,606

SPEED BAROMETRIC ALTITUDE AND AIRPLANE ACCELERATION RESPONSIVE FUELCONTROL Filed May ll, 1945 2 Sheets-Sheet 2 INVENTOR.

Patented Jan. 16, 1951 SPEED BAROMETRIC ALTITUDE AND AIR- PLANEACCELERATION RESPONSIVE FUEL CONTROL Stanley M. Udale, Detroit, Mich.,assignor to George M. Holley and Earl Holley Application May 11, 1945,Serial No. 593,214

This application -is a continuation in part of my copending application,Serial *,No. 582,266, led March 12, 1945. f

The object of this invention is to control the fuel supply of an engineby the density of the air and the speed of the engine. These devices areknown as speed/density fuel supply devices. If such a device isinstalled on an airplane engine and if the airplane is dived, thevincrease in air .density during the dive causes the engine tooverspeed, and it is desirable therefore to restrict the fuel supplytemporarily during the acceleration period and to allow ,the fuel supplyto gradually increase to the desired amount after the plane has leveledoff and the dive is over.

Fig. 1 shows diagrammatically the preferred form of my invention.

Fig. 2 shows the control applied to a, well known type of airplaneengine. y

In Fig. l, Ill is the fuel entrance, II is the fuel exit to the engine,not shown, I2 is an.

engine-driven fuel pump, whichv delivers each revolution an amount offuel determined by the position of the control lever I3, III is a leverconnected at one end to a barometric-responsive servomotor piston I5 andat the other end to the engine speed-responsive piston I6. h

An altitude or barometric element Il is arranged so as to move theservomotor valve I8, which controls the movement of the piston I5 in awell-known manner. An engine-driven pump I 9 circulates operating oilpast a temperatureresponsive heating element 20. This operating oiloperates in a closed system out of communication with the fuel oilsystem and is used only as part of the hydraulic or servomotor controlsystem. When viscosity is high and temperature low, element 2@ operatesso that the effect of viscosity is temporary and is quickly correctedbecause of the electric heat available when the temperature is low andalso' because the operating oil is selected so as not to be toosensitivev to temperature changes as far as viscosity is concerned. Theelement 28 is of a well known type in which a bimetallic element isheated by electricity until the circuit is broken by the deflection ofthe bimetallic element and thus the iiow of electricity is discontinuedwhenever the temperature in the reservoir I2 exceeds a predeterminedminimum temperature.

This oil under pressure from pump I9 is conveyed through a passage 2land a bypass 68 to cylinder 22 above speed-responsive piston I6. Arestricted opening 23 in piston I6 allows this 1 Claim. (Cl. 60-41)needle 25 is controlled by lever 26, which is moved by the servomotorpiston I5.

AV restricted inlet 21, above the piston I5, leads from the oil pressurepassage 2I into cylinder of the piston I5 whenever the valve I8 movesaway from its neutral position in which it is shown. Whenever the valveI8 departs from its neutral position relative to the piston I5 oil underpressure iiows from one or the other end of the cylinder 28, throughoneor the other of the two restrictions 2'I or 29 and then past'the valveI8 to the passage 30 and so back to the reservoir 52. This valve I8 isjust small enough to move freely through the central opening in thepiston I5 but is large relative to the orices 28 and 29. Passage 30-also delivers the oil flowing past the needle valve 25 from the cylinder22, which iiows through the opening 23 and past the piston I6.

The pressure generated by the pump I9 is determined largely by therestriction 33, which is considerably larger than the restriction 23.The oil under pressure in chamber 22 compresses a spring 3i, whichsupports piston I6. An adjust- 1atlilestop 32 limits the upward travelof the pis- An inertia-responsive valve 3d is shown in the position itassumes at low acceleration when it is held open'by the spring 35, whichspring is overcome by acceleration above a predetermined value, whichvalue is set by the stiiness of spring 35. The direction of motion is tothe right as shown by the arrow below the needle 25. Hence, duringacceleration, the inertia valve 36 moves to the left, stretching thespring 35 and preventing the flow past the needle 25. The pressure belowthe `piston I6 then becomes equal to the pressure above .the restriction23. The spring 3l then raises the piston I6 against the stop 32, whichraises the left-hand end of the lever III, which raises the lever I3clockwise, which re- -duces the discharge from the fuel pump I2, so

that during acceleration to the right, Athe lefthand of the lever III isheld in the position corresponding to a minimum revolution per minute'of the pump I9 as far as the speed control is concerned. The servomotorvalve I8 is rst moved by the barometric elements II and the piston I5follows, being moved hydraulically by the pressure difference resultingfrom the displacement of valve I8 until the piston is restored oil toiiow past a needle 25 in outlet 24. The 5g to the neutral positionrelative to its servomotor valve I8. When the piston I8 seats on thestop 32 the fuel supply per revolution is held at a low value and thefuel supply is controlled solely by the barometrically-responsiveservcmotor valve I8 and its piston I5. In Fig. 2, 50 is the combustionchamber. 52 is the ,fuel nozzle connected to the outlet-II of the fuelpump I2. 54 is the air compressor supplying compressed air to thecombustion chamber 50. 56 is the gas turbine driving the compressor 54.58 is the conical outlet from the gas turbine. SII and 82 are the driveshafts to the fuel pump I2 and to the oil pump I9.

Operation `safely be burnt. The pump I2 being rotated at engine speed(or at a fraction thereof) discharges fuel at a rate proportionate tospeed. The barometric elements I1 move the servoinotor` valve I8 whichcontrols the movement of its servile piston I which controls the strokeof the pump through vthe lever I3. The downward movement of the pistonI6 also controls the stroke of the pump through the lever I3. When theinertia valve 34 moves to the left therefore, the piston I6 no longerresponds to speed but to the spring 3| which causes the piston I8 toengage with the adjustable stop 32. Thus the rise ofthe piston I6 tendsto reduce the fuel per revolution when the acceleration exceeds a safefigure. The expansion of the element I1 'with altitude tends to decreasethe fuel fiow per-revolution. Normallyfwhen running at any constantspeed, the position of the lever I4 is determined by the altitude,because as the altitude increases, the element I'I expands downwards andthe servomotor valve I8 rises and the piston I5 also rises due to theactionof the valve I8 releasing the pressure in cylinder 28. The tworestricted openings 21 and 29 ensure that the pressure above and belowthe piston I5 are always the saine when the valve I8 is in the neutralposition (in which it is shown) as then the leakage past both the upperand low portions of valve I8 causes equal flow through 21 and 29 whichare of equal size. rl'he `slightest departure of the servomotor valve I8from this neutral position upsets the equilibrium, as once the valve I8descends there is a flow through the opening 29 many times greater thanthe flow due to leakage through 2'I andv then the pressure` below thepiston immediately falls and the piston I5 descends quickly` the enginespeeds up above a predetermined speed, the piston I8 departs from thestop l2 and the lever I4 is moved down and the lever I3 is movedcounter-clockwise to increase fuel flow. Hence, at high speed,the/discharge from pump I2 is determined by the altitude and by thespeed of the engine. During acceleration, altitude is the only variablewhich controls fuel discharge per revolution of the engine as the speedis no longer a factor as the inertia valve 84 neutralizes the speedcontrol of the fuel pump I2. The engine can be either an internal or anexternal combustion engine. The most modern engines in use today inairplanes are of the external type. The/external combustion engines inuse today on airplanes are almost always gas turbines.

The fuel flow control lever I8 and hence the fuel flow per revolution isthus responsive to:

(a) Altitude through the barometric element u, servomotor Vvalve I8 andservomotor piston (b) Engine revolutions per minutey through the pistonI6, restriction 23 and needlevalve 25, which in its turn is controlledby the altitude responsive piston I5. v

(c) Acceleration which renders (b) ,inoperlative so that duringacceleration, the .fuel ficw per revolution is controlled only by thealtitud:

This device is particularly adapted to control the fuel supply to a gasrturbine in which the turbine drives the oil pump I9 and the fuel pumpI, I2 at a speed proportional to the speed of the turbine.` Gas turbinesare particularly susceptible to excessive speeds.

WhatIclaimis:

Fuel control means for an engine having an engine driven fuel meteringpump for supplying fuel to the engine when driving an airplanecomprising engine speed responsive means driven by said engine andconnected to said pump so as to increase its delivery as the speed ofthe engine increases, a barometric element also connected to said pumpand adapted to decrease the delivery of said pump as the altitudeincreases. inertia responsive means responsive to the acceleration ofthe airplane adapted to render the speed responsive means temporarilyless effective during acceleration.

STANLEY M. UDALE.

REFERENCES CITED The following references are of record inthe le of thispatent:

UNITED STATES PATENTS Number Name Date 2,276,794 Ricci Mar. 17, 19422,278,493 Samiran et al. Apr. 7, 1942 2,296,876 Samiran et al Sept. 29,1942 2,353,269 Roth et al. July 11, 1944 p `FOREIGN PATENTS NumberCountry Date 526,988 Great Britain Sept. 30, 1940

